The present invention relates to an automatic transmission network restoring system and, more particularly, to a system for automatically restoring a transmission line in trouble in a communication network comprising a synchronous optical transmission network, a plurality of nodes having a function of controlling the switching of a plurality of path terminating points for a synchronous transmission signal path add/drop function, and a network controller for controlling the whole communication network with the synchronous optical transmission network and nodes.
This type of synchronous optical transmission network is called SONET (Synchronous Optical Network), and FIG. 14 shows the schematic system structure of the system. Referring to FIG. 14, the system comprises DCSs (Digital Cross-connect Systems) 2-1 to 2-6 and ADMs (Add-Drop Multiplexers) 3-1 to 3-10 provided on transmission lines connecting adjacent ones of the DCSs 2-1 to 2-6. The ADMs 3-1 to 3-10 are nodes basically having the add-drop function with respect to the signal path called STS (Synchronous Transport Signal) path. FIG. 15 shows a specific example of node structure.
The node structure as illustrated comprises terminals 30a to 30c, as shown in FIG. 2. The terminals 30a to 30c have the same structure, and only the terminals 30a and 30b are shown in detail for the sake of brevity. Physical terminal parts 31a and 31b convert the optical signal inputted to the ADM 3 into the electric signal and also convert the internally generated electric signal into the optical signal to be transmitted to the outside.
Section terminal parts 32a and 32b insert and extract a section over-head into and out of the transmission signal. Line terminal parts 33a and 33b insert and extract line over-head into and out of transmission signal. Line protection switching parts 34a and 34b select normal one of prevailing system/spare system optical fibers having a redundant system switching structure by using K1 and K2 bytes as APS bytes of APS (Automatic Protection Switching) protocol processing transferred between opposite ADMs. STS pointer processing parts 35a and 35b take out the STS payload envelope with H1 and H2 bytes in the line over-head and add an appropriate over-head containing H1 and H2 in the STS payload.
STS path terminal/monitor parts 36a and 36b take out and insert the path over-head from and into the STS payload envelope. An STS path switch 42 is a matrix switch having pluralities of STS payload capacity input and output terminals, and it can connect and disconnect the input and output terminals of the terminals 30a to 30c. The STS path switch 42 has a plurality of path terminal points IDo to IDn, which are switching controlled for inputting and outputting the data to and out of them. For the switching control of the terminal points IDo to IDn, an identifier ID specifying each of these terminal points is preliminarily provided to each thereof, and each terminal is hereinafter represented by the identifier ID.
An STS path control part 37 receives the STS path switch setting control command from a network controller 1 (see FIG. 1) for controlling the entire communication network for controlling the STS path switch 42, as well as updating data in an STS path setting data memory 371 for reflecting the prevailing (i.e., newest) connection status of the STS path switch 42.
A path terminal controller 38 reflects the path over-head status monitored by the STS path terminal/monitor parts 36a and 36b on the path terminal point control data that are stored in a path terminal point control data memory 381, and provides the data in response to the path terminal point control retrieval requests from the network controller 1 (see FIG. 1).
A line terminal point control part 39 reflects the line over-head status monitored by the line terminals 33a and 33b on the line terminal control data, and provides the data in response to the line terminal point control data retrieval requests from the network controller 1.
In a case of such system using ADMs, in which a path 101 is set between the ADMs 3-1 and 3-3 as shown in FIG. 14, in the STS path switch 42 of the ADM 3-1 the path 101 is set in that the path terminal points IDo and IDi are connected to each other. At this time, data indicating that the terminal points IDo and IDi are in connection with each other, is stored as STS path setting data in the STS path setting data memory 371 of the STS path controller 37.
In such prior art SONET, a trouble which occurs in any of the paths set between adjacent ones of the DCSs 2-1 to 2-6, can be coped with an automatic network restoration (TRANS) function, which is previously assembled in each DCS, and pertaining techniques are disclosed in Japanese Laid-Open Patent Publication No. 60-22848 and Japanese Laid-Open Patent Publication No. 64-23647.
In such prior art techniques, only paths that are set between adjacent DCSs are capable of automatic restoring by the automatic communication network restoring function. In the actual SONET, as shown in FIG. 14, the communication network includes not only DCSs but also ADMs, and a path may be set between adjacent ADMs (such as one showing as working route 101). In the prior art system, therefore, when a transmission line trouble A (see FIG. 14) takes place in the path 101 set between adjacent ADMs, the path 101 can not be restored by the prior art process of automatic restoration of path between adjacent DCSs.